1. The Identification of Colour Photocopies A Case Study การจำแนกเครื่องถ่ายเอกสารสี : กรณีศึกษา C.K Li and S.C. Leung Forensic Science Division, Government Laboratory, Ho Man Tin Government Offices,88,Chung Hau Street,Ho Man Tin, Kowloon, Hong Kong

2. Introduction The photocopy machine has essential Office equipment in modern times. The high quality of reproduction of document has resulted in a more extensive usage of colour photocopying

3. Photocopy

4. Case : counterfeit Hong Kong ( a Rank Xerox A- colour 635 photocopier ) Examination : microscopic counterfeit repeated dotted patterns to identify the colour photocopier

5. Method and Materials Dotted patterns on colour photocopies : Series of repeated patterns of yellow dots - model the photocopying machine - to identify

6. Figure1 three images of Hong Kong $500 on A4 paper

7. The yellow dots were too pale to be clearly seen the naked eye / a hand lens used VSC : patterns on counterfeit with blue light and filter at 610 nm

8. เครื่อง VSC

10. Figure 2 illustrates one complete unit of the patterns as visualized in the monitor of the VSC

11. Results and Discussion Suspected : a Rank Xerox A color 635 photocopier printing the counterfeit. Specimens : sheets of control prepared with this photocopier

12. Dotted patterns : electronic devices in the machine during the photocopying process Ques : patterns unique, utilized to prove that photocopying was produce the counterfeit ? Ans : survey was colour photocopies by machines commonly available in Hong Kong

13. Survey on colour photocopies Table1. A summary of a survey on the presence of regular dotted patterns on colour photocopies made by Rank Xerox,Canon and Ricoh photocopierss

14. Figure 3. Arrangements of the dotted marks Depicted in sample Photocopies from three of photocopying machine

15. Figure 4. Arrangement of repeated dotted motifs present on a photocopy as visualized in the monitor of the VSC

16. Figure 5. Example of the dotted motifs depicted from Cannon colour copiers

17. Conclusion Dotted patterns counterfeit control specimens (Rank Xerox Acolor 635 photocopier) consistent in terms of size and arrangement

18. patterns  serial numbers machines  identifying the photocopiers (arrangements of the dots in the 8x15 grid unit cells.)

19. Results from the survey ‘identification marks’ on the photocopies are unique for a particular copying machine. : Xerox(Hong Kong) Ltd. Patterns of dots represent the serial numbers that identify : Canon CLC350, CLC700 and CLC800 colour copiers also serve as identification codes

21. Q & A